1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device in which a wire is bonded to a bonding pad of an interconnection.
2. Description of the Related Art
Along with micropatterning and high-density integration of semiconductor devices, interconnections are also micropatterned and multilayered. However, micropatterning and multilayering interconnections decrease electromigration resistance and stress migration resistance. To avoid this, an aluminum-copper alloy is being used as a material of an interconnection instead of pure aluminum or an aluminum-silicon alloy which has conventionally been used.
One related art of a method of manufacturing a semiconductor device in which a gold wire is bonded to a bonding pad of an aluminum-copper alloy interconnection will be described with reference to FIGS. 1A to 2B. In this related art, as shown in FIG. 1A, an aluminum-copper alloy interconnection 12 having a bonding pad 12a is formed on an interlayer insulating film 11 on a semiconductor base (not shown). An insulating film 13 such as an SiO2 film is deposited by CVD to cover the interconnection 12.
As shown in FIG. 1B, a photoresist film 14 is applied to the insulating film 13, and an opening 14a is formed in the photoresist film 14 above the bonding pad 12a by photolithography. As shown in FIG. 1C, an opening 13a is formed in the insulating film 13 by etching using CFX-based reaction gas and the photoresist film 14 as a mask.
To vertically etch the insulating film 13 in forming the opening 13a, anisotropic etching is employed to form an organic polymer film 15 and metal polymer film 16 on the inner side surface of the opening 13a during etching, and to progress etching using the organic polymer film 15 and metal polymer film 16 as a mask.
The organic polymer film 15 is made of a reaction product upon reaction between the reaction gas and the materials of the photoresist film 14 and insulating film 13, contains many organic components, and is formed before the interconnection 12 is exposed. The metal polymer film 16 is made of a reaction product upon reaction among the reaction gas, the aluminum-copper alloy and the materials of the photoresist film 14 and insulating film 13, contains many metal components, and is formed after the interconnection 12 is exposed.
Even when the photoresist film 14 is removed with an organic solvent while the organic polymer film 15 and metal polymer film 16 are kept formed, they are not removed. The organic polymer film 15 and metal polymer film 16 are left on the inner side surface of the opening 13a or scattered onto the bonding pad 12a. 
If a gold wire is bonded to the bonding pad 12a in this state, the bonded gold wire easily peels off because the organic polymer film 15 and metal polymer film 16 left on the inner side surface of the opening 13a decrease the bonding area or the organic polymer film 15 and metal polymer film 16 scattered onto the bonding pad 12a interfere with bonding.
In this related art, therefore, the photoresist film 14 in the state of FIG. 1C is removed by a predetermined thickness with the oxygen plasma. Then, as shown in FIG. 1D, the remaining photoresist film 14 and metal polymer film 16 are removed with an amine-based organic solvent. As shown in FIG. 2A, the organic polymer film 15 is removed with the oxygen plasma. As shown in FIG. 2B, a gold wire 18 is bonded to the bonding pad 12a via a gold wire bond 17.
In the above related art, however, since the photoresist film 14 is removed by a predetermined thickness with the oxygen plasma, and then the remaining photoresist film 14 and metal polymer film 16 are removed with the amine-based organic solvent, an aluminum oxide film has already been formed on the surface of the bonding pad 12a in removal with the amine-based organic solvent.
The aluminum oxide film functions as a mask against the amine-based organic solvent. Even by removal with the amine-based organic solvent, the aluminum oxide film remains on the surface of the bonding pad 12a, and the surface of the bonding pad 12a is kept smooth. In addition, along with micropatterning and high-density integration of semiconductor devices, the area of the bonding pad 12a and the diameter of the gold wire bond 17 are decreased.
For this reason, in this related art, the gold wire 18 bonded to the bonding pad 12a easily peels off. Therefore, the semiconductor device cannot be manufactured with a high yield. In addition, the area of the bonding pad 12a and the diameter of the gold wire bond 17 are difficult to decrease, and a fine semiconductor device having a high integration degree cannot be manufactured.
It is therefore an object of the present invention to provide a semiconductor device manufacturing method capable of preventing peeling of a wire bonded to a bonding pad of an interconnection to allow the manufacture of a semiconductor device with a high yield and to decrease the area of the bonding pad and the diameter of a wire bond to allow the manufacture of a fine semiconductor device having a high integration degree.
In the semiconductor device manufacturing method according to the present invention, a metal polymer film formed on the inner side surface of the opening of an insulating film by anisotropic etching of the insulating film is removed with an amino group (NH2xe2x80x94) in an amine-based organic solvent, while a photoresist film is removed with the organic solvent component in the amine-based organic solvent. This removal with the amine-based organic solvent is performed subsequent to anisotropic etching of the insulating film.
As a result, the bonding pad of an interconnection is free from any oxygen plasma processing till removal with the amine-based organic solvent after the bonding pad is exposed in the opening of the insulating film by anisotropic etching of the insulating film. No aluminum oxide film is formed on the surface of the bonding pad of the interconnection in removal with the amine-based organic solvent.
Along with removal using the amine-based organic solvent, the amino group (NH2xe2x80x94) in the amine-based organic solvent enters the interface between aluminum and copper of an aluminum-copper alloy in the bonding pad, and highly ionizable aluminum elutes. As the elution progresses, copper crystal grains come out of the aluminum-copper alloy to form pores in the surface of the bonding pad upon removal.
An organic polymer film formed on the inner side surface of the opening of the insulating film by anisotropic etching of the insulating film is also removed with the oxygen plasma, and then a wire is bonded to the bonding pad. In bonding, no metal polymer film or organic polymer film exists on the bonding pad.
More specifically, since no metal polymer film or organic polymer film exists on the bonding pad in bonding, the metal polymer film and organic polymer film do not decrease the bonding area or interfere with bonding. In bonding, since pores are formed in the surface of the bonding pad, the material of the wire bond enters these pores. Therefore, the wire bonded to the bonding pad of the interconnection hardly peels off.
Since the wire bonded to the bonding pad of the interconnection hardly peels off, the semiconductor device can be manufactured with a high yield, and the area of the bonding pad and the diameter of the wire bond can be decreased to manufacture a fine semiconductor device having a high integration degree.
In a preferred semiconductor device manufacturing method according to the present invention, the time for removing, with the oxygen plasma, the organic polymer film formed on the inner side surface of the opening of the insulating film by anisotropic etching of the insulating film is set to 10 to 40 min. The organic polymer film can be satisfactorily removed, while formation of the aluminum oxide film on the surface of the bonding pad can be reliably prevented even upon this removal.
For this reason, the wire bonded to the bonding pad of the interconnection more hardly peels off without any interference by the aluminum oxide film on the surface of the bonding pad.
Since the wire bonded to the bonding pad of the interconnection more hardly peels off, the semiconductor device can be manufactured with a higher yield, and the area of the bonding pad and the diameter of the wire bond can be further decreased to manufacture a finer semiconductor device having a higher integration degree.